/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/NiagaraSystemEditorDocumentsViewModel.h
[FScriptToolkitsActiveDocumentChanged](API\Plugins\NiagaraEditor\ViewModels\UNiagaraSystemEditorDocumentsVie-\FScriptToolkitsA-) & OnActiveDocumentChanged()